One of the peculiarities that allowed William Riker to discover that what he originally thought was the future was actually a fabricated reality was noticing that La Forge's level 1 diagnostic had lasted for more than 30 hours, displaying an uncharacteristic level of incompetence, as it would have never taken the real La Forge more than 4. (TNG: "Future Imperfect")

Locking a starship's transporters diagnostic mode, effectively putting it into a diagnostic cycle, will keep any inert matter in the pattern buffer. Ordinarily, inert matter can only remain in the pattern buffer for seven minutes before becoming irretrievably lost, but Montgomery Scott was able to reconfigure a transporter, locking the pattern into a level 4 diagnostic cycle to keep his pattern in the pattern buffer for 75 years. His pattern was retrieved with minimal degradation. However, another occupant was not so lucky and was lost. (TNG: "Relics")